Viscometer



Filed Jun@ l2. 1922 3 Sheets-Smet l'.

M139 @1 MILLER Lz@ VISGOMETER :Filed Jun@ 12. 1922 s shams-sham 2 A Al:viii m Y l @gg/MO5 S m9 @29V c. D. MILLER 1,727,836

4 vIscoMETER Filed June 12, 1922 5 Sheets-Sheet 3 fz/ezbf: Y Carl mi;

Patented Sept. 10, 1929.

UNITED STATES PATENT OFFICE.

CARL D. MILLER, OF WINNIPEG, MANITOBA, CANADA.

vrscomzarnn.

AApplicatiimiled .Tune 12, 1922. Serial No. 567,657;

The present invention relates to viscometers.

More particularly the present invention relates to methods and means formeasuring the viscosity of liquids and, though of gen- -25 the planemarked by the lline2-2 eral application, will be described moreparticularly with reference to the measuring of the viscosity of oils. A

An object of the present invention is to lo provide a simple and direct'method of'meastion of saidviscosity'..n y

A further Objectis to provide a continuouslyr perable, accurateapparatus' for f` erjobjects wlll T tion rocee'dsI uring viscosity. p

'A vfurther ob'ect is-'to provide a method for measuring the viscosityof liquids `,which method adapts itself to a cohtinuous indicavdicatirithe viscosity of liquids.

appear as the descrip'- Re erring to, the drawings-- j Figure 1 isaplan` view fof oneembodinient of the present invention l Figure 2 is asectional view'talren yalong of Figure 1;

Figure 3 .is a sectional view taken along the line 3-3of Figure 3U theplane marked Figure 7 shows a modification of the structure shown inFigure 1; andl Figures 8, 9, 10 and 11 are diagrams illustrating theprinciples of the present inven-l tion.

The principles of the present invention are based upon the tendency'. ofliquid to move along with solid `surfaces with which.

it. may be in contact.- According tothe present invention, the pressurecreated by this .action is measured. So longas the velocity of theliquid does not rise above a certain socalled critical velocity, the,motion of the.

liquid is what isknownas a stream line or non-sinuous motion. Under suchconditions, the pressure produced is proportional to the velocity of themoving solid surface and to the true viscosity of the liquid. For thepurpose of simplifying the indications, the velocity of the moving solidsurface may be kept substantially constant. Regardless of the liquidunder test, the pressure produced will be substantially proportional tothe viscosity of said liquid. Any convenient means for measuring saidpressure may be used and may be calibrated to indicate directly the'trueviscosity of the liquid under test, By using a manometer, the'liquid inwhich is the same as the liquid under test, the socalled kinematicviscosity of the liquid under testis indicated on an evenly dividedscale.

'By suitable calibration, indications according to'any L.arbitrarysystem, such as the Saybolt, Redwood, or Engler, may be had.

"1 Referring to Figures 1 to 7 of the ldrawings, an apparatus isillustrated having ay relatively stationary part within which revolves amovable part, said stationary and movable arts having space between them-in which 1s located the fluid, which may be oil, whose viscosity is tobe measured. The liquid isdrawn along through this space by rotation ofthe movable part. Means are providedfor checking the motion of theliquid whereby to produce a pressure in said liquid, which pressure maybe indicatedv by suitable means.

' The relatively stationary part of the ap- 4p'aratus illustrated inFigures 1 to 7 is indicated by the numeral 10, which memberv will be"referred to herein as the stator.

Snu'gly lfitting* witha running fit within the stator'lO is the rotor11;- VThe stator 10 and jrotor 11 are 'illustrated asf having conicalvcontacting surfaces, 'an annular space 12 being rovided between saidstator and rotor for t e reception of liquid. It will be under-y stood,ofcourse, that the term annular-7 is .usedin abroad" sense. Constructioninvolving eccentric'ity of the vbounding Surfaces of saidf'space 12 orvariationsffrom absolute uniformity of'dimension's ,of said space willnot depart from the scope of the invention.

lThenumeral 13 indicates a pipe connection whereby liquid may be ledinto the space 12. The numeral 14 indicates an outlet connec-4 tionleading from the annular space 12, said outlet connection 14 beingprovided with the outlet pipe 15. The out-let connection 14 may beprovided with the tube -16 communieating with the manometer tube 17. Theforce applied to the liquid which is effective in producing the pressureis applied in a direction which is tangential to the contacting surfacebetween liquid and solid. A

Located between the connections 13 and 14 is the filler or sto-p 18.According to the structure as illustrated in Figure 1, the inletconnection 13 is located in the region where the surface of the rotor 11is leaving the stop A 18 andthe outlet connection 14 is located in theregion where the surface of the rotor 11 is approaching the stop. Itwill be clear that instead of combining the outlet connection" may beseparate'and distinct. For example,

which the liquid mali7 the tube 16 leading to the manometer tube may beretained in the position shown anda separate outlet connection maybeplaced elsewhere in the periphery of the stator 10. Suitable positionsare indicated by the lines 19-19 and 20-20.

6, it will be noted that the stator 10 may be supported on standards21-21. The rotor kmay be mounted in any preferred way. Inasmuch assuitable mounting means will readily occur to those skilled in the art,it is considered unnecessary to describe saine in detail. The rotor 11may be rotated byv means of a driving bar 22 mounted on the end of thedriving shaft 23. Said driving bar contacts with the upstanding ins24-24 which project from the upper si e of the rotor 11. Though the typeof drive is Subj ect to wide variation, the one illustrated has theadvantao'e that it permits the rotor to bear properly in t e stator andeliminates lateral pressure from the driving mechanism. y t

A. feed tube 25 ma be provided through e conducted to the inletconnection 13. iquid may be conducted to the inlet connection 13 at arate somewhat faster than said liquid is actually conducted through theinstrument, the excess liquid dripping over the connection 13 into anysuitable receptacle laced below said 'connection 13. Figure 6 ilustrates drops of liquid fallno from the feed tube 25,excess.dropsfalling be ow the connection 13. This construction insures a su-cientsupply of liquid at 'a' constant level and consequently a cOnStant'preS- sure, thepressure of thesupply beingdetervmined bytheheight of the overflow. surface, which height is al ected only veryslightly by variations, within limits, inthe amount of liquid comingfrom the feed tube 25. v Freferably the outlet terminal 26,'of theReferring now more particularly to Figure outlet -tube 15 is on the samelevel as the inlet, a construction which is desirable for the purpose ofeliminatingthe effect of gravitational The pressure of the liquid in thespace 12 v in the region at which the surface of the rotor isapproaching the stop 18 is indicated by means of a pressure gauge, whichmay consist of a mercury manometer tube, which tube may be so designedthat the surface of the mercury, when no pressure is being developedwithin the viscometer, is on a level with the inlet connection 13 andthe outlet terminal 26. It will be understood that proper allowance mustbe made for the effect of the liquid under test in the pressure arm ofthe manometer tube. If preferred, the necessity for making thisallowance may be avoided by connecting the other arm ofthe manometer tothe inlet and having -it filled with the liquid under test as far asvthe mercury, in which event there is no object in having the surface ofthe mercury, when no pressure is being registered, on a. level with theinlet connection 13 and outlet connection 15. If for any reason it ispreferred to have the inlet connection 13 and outlet connection 15 atdifferent levels, the readings of the pressure gauge should be correctedby adding or subtractin a certain pressure, which may be determine byallowing liquid to pass through the instrument under the influence ofgravity only, the rotor being at rest. It will be understood, moreover,that instead of 'using mercury in the manometer tube, the rise oftheliquid under test in the open arm may be used to indicate pressure.

The invention adapts itself for use with any of the types of pressuregauge known in the art, including indicating and recording gauges andincluding gauges of the relay type.

The structure referred to in the discussion of Figure 6, in which theliquid under testv (instead of mercury) is used'in the manometer tube17, is convenient in giving a direct indication of the ratio betweencoetlicient of viscosity, (so-called absolute viscosity) and density.Indicating the co-efficient of viscosity (absolute viscosity) by theletter n and the density by the letter D, said structure renderspossible the determination of n over D by direct reading. It will benoted that the open arm of the manometer tube 17 is provided withgraduations, which ma be utilized for this purpose.

1 y using mercury or other relatively heavy lll) material differing fromthe liquid under test in the inanometer tube 17, pressure is measuredina way that the density bf the liquid under test has little orno effecton the scale reading.A Under this condition, the values of m'ibsoluteviscosity) are indicated directly.

@Figure 7 illustrates an adjustable outlet connection, the outow ofliquid being controlled by the needle valve 27, the position of whichmay be controlled by the handle 28.

- the oil.

U Figure 7 a illustrates the modification hereinabove referred to inwhich outlets are provided between the inlet 13 and the pressure -lgauge connection 14; Two such outlets are. shown, whichy bear thenumerals 29 and 30.

There is Aalso the outlet provided'through the Vpressure gaugeconnection 14, which commuv-nicates with the tube 15.l Avery important fresistance, which may be considerable, and

which may vary considerably from time to time even with no change inthecharacter of p In ractice the instrument ill be held at a denitetemperature, at vw ich it measures the viscosity of the oil.I Thetemperature of the oil to be tested will in practice be at thetemperature of the instrument as it enters the annular space 12. Thesuction required to draw the'oil through the inlet d epends upon thetemperature at which the oil is supplied, since this affects thethickness of the oil as it enters. This suction is all taken upl betweenthe inlet, and the first of the outlets 29 or 30 that is open, and itdoes not affect the :pressure developed at the connection 14. Ac-

cording to the present invention, if a different liquid ,is delivered tothe machine', it will auto- .,matically replace the liquid previouslydelivered, and the pressure gauge will thenindicate the viscosity of theliquid being fed in. Outlet 29 may be open, and both outlet 30 I andtheoutlet through the tubey 15 may be i pressure gauge connection 14 isabout twice' closed. This will give thehighestrange of pressure; oroutlet may be open andoutlet 29 and connection 15 may be closed, givingpressures onlyl half as great, and, with the same pressure gauge,permitting the measurement of viscosities twice as great as in the casewith outlet.v 29 open and outlet 30 and connection 15 closed; or, witheither outlet 29 or outlet 30 open, the oil may be allowed to' ,flowthrough the tube 15 with nothing but the lrictional resistance of thetube to4 oppose the flow, and still lower pressures obtained,

permitting the measurement lof'still lower viscosities with the samepressure gauge With the givenoil at the same temperature, the

v pressure developed with only outlet 29 open is about twice as greatlas that with only outlet 30 open, since theJ length of the annularpassage12 from outlet 29 around to the that from outlet.A 30 totheconnection 14,.

With iow throu hv the tube 15, the pressure developed depends upon theresistance` offered by the tube to the passage of the oil, and this udepends uponthe lengthwand diallneter of the tube. It can readily bemadaawysmallfrac-I tion of the pressureavithfonly outlet ,appearpermitting the measurement-'of corrl 'pondescaping ingly greaterviscosities without change of ment, but one outlet is required, but itmust be between the inlet 13 and the pressure gauge connection A14 tomake the pressure developed independent of the suction required toovercome the inlet resistance. v

The performance of the described embodiment of the present invention maybe illustryated by means of the diagrams illustrated in Figures 8 to 11inclusive, which diagrams show the conditions of.liquid containedbetween relatively movingsolid surfaces. The liquid which is indicatedby the letter L is contained between the surfaces S-l and S-2, the uppersurface S-2 having a motion to `the right in Figures'8, 9, 10 and 11, asindicated by the double-headed arrows. In Figyure. 8 the liquidencounters no obstruction, the only hindrance to its motion along withsurface S--2 being its adhesion to the stationary surface S-L The motionof the liquid in the various strata is illustrated by singleheadedarrows, said motion varying uniformly between said surfaces S--l andS-2. In Figure 9 the surfaces S-l and S-2 are both stationary and the liuid flows to the left under the influence o the pressure at the right.According to the diagram shown in Figure 9, the motion of the liquidincreases gradually from that at the surfaces S-l or' S-2 to a maximummidway between them. Figure 10 represents the combined motionsillustratedlin Figures 8. and 9 .andillustrates 'the resultV of thecomplete stoppage of the liquid' by the stop 18, it being assumed thatthe stop is applied to the stationary surface S-.1 somewhere at theright of the figure. According to the diagram shown in Figure 10, thereis a motion to the right of the liquid. adjacent to the upper surfaceS-2, which motion falls oli rapidly to zero at a point above the middle,and below this .poinst the motion is to the left, as indicated by th'esingle-headed arrows. The llow to the right is exactly balanced by the.iiow to the, left, the

result" being a circulatinginotion of the liquid, the upper 4layers ofwhich move along-withthe upper surface S-2 to the point of stop age, theliquid returningv along the lower sur aceS-'TL Figure 11 illustrates theeiect.. of partial stoppage ofthe liquidt In'thisfigure the curve markedf.=l shows the'motion-'obtained 'in the case of complete stop age, alllof the liquid carried to the right by t e direct effect o S-2 beingreturned by the efect` of thepressure created.y The curve :marked4 f=3/4 illustrates the casein which 3/4,of the liquid is i returnedby thepressure, 1 of said liquid throughV theloutlet.v `1 The curves lll themotion of surface .marked f=l f= andi-the straight line marked f=0`.appl-y similarly. Itf ma ybe giro-ted` that 'when )ii-ia large parte'the 'liquid ,.nearthe stationary *surfacev S-l is in l are, generallqy7speaking, preferable to values between l and 3/4. For the position ofthe partsas illustrated in Figures 1 to 6 inclusive,

. the outlet tube is preferably-of such length and diameter that f isnot over The flow of liquid between the rotor l1 and stator 10 isrepresented throughout by a curve correv spending-to the particularvalue of f. For

' the outlet connection at the position 19--19 or 20-20 of Figure 1, thepreceding statementshold with regard to that part of the liquid betweenthe inletl and outlet connections, but for the part from the outletconnection to the gauge connection and the stop 18 the flow isrepresented by the curve marked f=1. With the outlet connection in sucha position as that illustrated bythe line 19-19, parts being adjusted asabove referred to, there is no complete circulation of the liquid, theliquid which returns from the stop passing through the outlet andv notreturning again to the stop.

The diagrams showing the motion of the y liquid are based upon thefollowing formulae:

Let a represent the distance between the surfaces; the distance betweenthe stationary surface and any layer in the liquid; V, the velocit ofthe moving surface;.o, the velocity ofy any layer in the liquid; fw, thedimension of the liquid stream perpendicular to the plane 'of thediagrams; Q, the volume of li uid which flows in unit time under thecondition of unobstructed low,'as illustrated in Dia ram A; f, thefractional part of Q, which ows in the' opposite direction to that ofthe moving surface, because of the pressure dcreated by obstruction tothe flow which gqles'directly along with the moving surface.

faggi.; e whew/ae (e With regard to the,- outlet tube, let Z denote itslength vand d its diameter. The volume (1- fx@ of liquidv asses throughit 1n unit time under the in uence of the pressure p.,

cia3 1 a3 T= (l W (7) The preceding formulae are given for the'centimeter-gram-second, or c. g. s. system of units. Q is in cubiccentimeters per second, lw and a are in centimeters, and V and lv are incentimeters per second, :z: is in centimeters, f is a pure number, L, Z,cv and b are in centimeters, p is in dynes per square centimeter, and itis in the c. g. s. unit of viscosity, sometimes called the"poise. Theso-called dimensions of n are given by [nl [MDT-1l (8) Theproportionality constant may he cal-y culated, approximately, by theformul here given, and it may be determined with more exactness byexperiment with liquids of known viscosity. For the proportionality tohold, there are two limitations on the velocity of the liquid. One,mentioned pre viously, is that the critical velocity should not beexceeded. That is, the How must be of the stream-line type, and notsinuous'or turbulent. The other is that the force or pressure expendedin overcoming the inertia of the liquid,`should be negligible ascompared to that expended in overcoming the resistance due to theinternal fluid friction, or viscosity, of the liquid. In setting inmotion a stream of fluid, the force required to overcome the inertia ofthe fluid is given by F =du2A (9) in which F is the force in dynes, d isthe density in grams vper cubic centimeter, 4u is the average squaredvelocity in centimeters per second, and A is the crosssectional area ofthe stream, in square centimeters. force F is distributed over the areain which it acts, ina way corresponding to the velocity l lof the streamat different points.

If the effect of this force is not negligible, correc- The' said regionof checking.

tion can be made for it. This correction is particularly simple forliquids such as oils, all having approximately the same density, d. Forin nthis case, considering the velocity u to be the same, and A beingthe same, the force F is constant, and the net result is that a fixedcorrection is to be applied to the reading of the pressure gauge. Acorrection of this nature is sometimes referred to as a cor-v rectionfor kinetic energy.

In many cases it is necessasry to/regulate the temperature of liquidunder test in order to maintain said temperature at a substantiallyconstant value. For this purpose the instrument may be immersed in aliquid such as oil. One important advantage produced by the presentinvention is the fact that, regardless of the viscosity' of the liquid,the rate of flow is constant, assuming constant velocity of the rotorll, as diagrammatically indicated in Figure 8. This advantage may beutilized in procuring test readings according to arbitrary scales, suchas the Saybolt, Redwood, or Engler, referred to above. It

should be noted that the means for opposing a frictional resistance tothe flow of liquid under test results largely from frictional forceswithin the liquid,'rather than from the inertia of the liquid.

i claim:

l. The method of measuring the viscosity of a liquid which consists inadmitting said liquid between two surfaces in contacting relation witheach of said surfaces, said surfaces being adjacent through extendedareas, one of said surfaces moving relative to the other, checking theiiow of said liquid, allowing said liquid to pass out from between saidsurfaces at a regionV between the regions of inlet and checking of saidliquid, and meas- -uring the resulting pressure in said liquid at saidregion of checking.

2. The method of measuring the Viscosity 'of a liquid which consists inadmitting said liquid between two surfaces in contacting relation witheach of said surfaces, said surfaces being adjacent through extendedareas, one of said surfaces moving relative to the other, checking theflow of said liquid, allowing said liquid to pass out from between" saidsurfaces at a region between the regions of inlet and checking of saidliquid under substantially the same gravitational force under which4said liquid wasv admitted, and measuring the resulting pressure in saidliquid at 3. Apparatus for Ymeasuring the viscosity of a liquidcomprising a rotor and a stator having adjacent surfaces providing anannular space, means for-introducing liquid to said space, means forleading liquid from said space, means for measuring the pressure oftheliquid within said space, and means for checking the iiow nfsaidliquid Within said apparatus.. A

4;. Apparatus for measuring the viscosity of a liquid comprising a rotorand a stator' providing between them a liquid receiving passageway,means for conducting liquid to said passageway, means for conductingliquid from said passageway, liquid checking means between said inletmeans and said Aoutlet means, and meansffor measuring the pressure ofthe liquid within said passageway.

5. The method of measuring the viscosity of a liquid which consists inapplying said liquid` with a constant gravitational force to two opposedsurfaces having relative to one another a substantially constantvelocity, causing .the flow of said liquid to be checked, causing saidliquid to be delivered from between said two surfaces at a regionbetween the regionof application to said surfaces and the region ofchecking the flow of said liquid, and measuring the pressure createdwithin said liquid at the region of checking the flow of said liquid.

6. The method of measuring the viscosity of a liquid which consists inapplying said liquid to two opposed surfaces having relative to oneanother a substantially constant velocity, causing the flow of saidliquid to be checked, causing said liquid to be delivered from betweensaid two surfaces at a region between the region of application to saidsurfaces and the region of checking the flow of said liquid, andmeasuring the pressure created within said liquid at the region ofcheckinor the How of said liquid.

Apparatus for measuring the viscosity of4 a liquid comprising a rotorand a stator having adjacent surfaces providing an annular space, meansfor introducing liquid to said space, means for leading liquid from saidspace, means for checking the iiow of liquid Y of a liquid comprising arotor and a stator,

said rotor and stator providing between them an annular passageway,means for conducting liquid to said passageway with a substantiallyconstant gravitational force, means for conducting liquid fromb saidpassageway at a level at which the gravitational force is substantiallyequal to that at which liquid is conducted to said passageway, means insaid passageway for checking the flow of said liquid, and means formeasuring the pressureof thev liquid within said passageway, said Ameansbeing disposed adjacent to said checking means, said means forconducting liquid from said passageway being disposed between the meansfor conducting liquid to said passageway and said measuring means.

izo

9. Apparatus for measuring the viscosity causing said liquid to bedelivered from beof a liquid comprising two members having tween saidtwo surfaces, and measuring the coo erating circumferential surfacespropressure created within said liquid at the reviding between them anannular passageway, gion of checking the flow of said liquid. and meansfor moving one of said members Signed at Chicago, Illinois, this 9th dayof relative to the other whereby'to impart mo-` June, 1922.- tion to theliquid in said passageway. CARL D. MILLER.

l0. Apparatus for measuring the viscosity of a liquid comprising a rotorand a stator, said rotor and stator providing between them an annularpassa eway, means for conducting liquid to sai passageway with asubstantially constant gravitational force, means for conducting liquidfrom said passageway at a level at vwhich the gravitational force issubstantially equal to that at which liquid is conducted to saidpassageway, means for driving said rotor, and means for measuring thepressure of the liquid within said passagewa i n ll. Apparatus formeasuring the viscosity of a liquid comprising a rotor and a stator,said rotor and stator providing between them an annular passageway,means or conducting liquid to said passageway with a substantiallyconstant gravitational force,-means for conducting liquid from saidpassageway at a level at which the gravitational force is lsubstantially equal to that at which yliquid is conducted to saidpassageway, means' for drivin@ said rotor, means for checking motion oi7liquid within said passageway, and A means for measuring the pressure ofliquid within said passagewa said checking means being located adjacento `and between said inlet means and said pressure measuring means. 12.The method of measuring the viscosity of a liquid which consists inadmitting said liquid between two surfaces in .contacting re ation witheach of said surfaces, said surfaces being adjacent-through extendedareas, one of said surfaces movin relative to the' otherchecking the iowo said liquid, a1- lowing said liquid to pass out from between saidsurfaces, and measuring the resulting pressure in saidliquid at saidregion of" checking.

13. The method of measuring the viscosity of a liquid which consists inadmitting said vliquid between two surfacesl in contactingrelation witheach of said surfaces, said sur. faces being adj acentethrough extendedareas, one of said surfaces moving relative to the other, checking theiiow of said liquid, allowing said liquid to ass out from between saidsurfaces under su stantially the same gravi-v tational force under whichsaid liquid is admitted, andmeasuring .the resulting pressure in saidliquid at said region of checking.

. 14. The method of measuring the viscosity of a liquid which consistsin applying `said liquid with a constant gravitational Vforce .totwo'opposed surfaces having relative to one another a substantiallflyconstant velocity,

causing the fiow of said liquid to be checked,

